Non-contact printers which utilize charged droplets are generally known in the art as shown by U.S. Pat. Nos. 3,373,437 to Sweet et al; 3,560,988 to Krick; 3,579,721 to Kaltenbach; and 3,596,275 to Sweet. Typically, fluid filaments of ink, dye or the like pass through the orifices of an orifice plate having an array of individually controllable electrostatic charging electrodes disposed downstream of the orifice plate along the "droplet formation zone". In accordance with known principles of electrostatic induction, each fluid filament assumes an electrical charge opposite in polarity but related in magnitude to the electrical charge of its respective charging electrode. When a droplet of fluid separates from the filament, an induced electrostatic charge is trapped in the droplet. Subsequently, the charged droplet passes through an electrostatic field of vector quantity which is oriented so that the droplet is deflected from the normal path towards the droplet catching structure. Uncharged droplets proceed along a normal path and are deposited upon a receiving substrate.
Recently, it has been proposed to utilize ink jet devices as a means &:o print patterns or the like on textile materials using apparatus such as that described in commonly-owned U.S. Ser. No. 428,490 to Gamblin, the disclosure of which is hereby incorporated by reference. In order to achieve fine printing of patterns on a textile substrate, it is necessary to utilize an orifice plate having a much longer linear array of very small orifices sized in the range of, for example, 0.00035 to 0.020 inch diameters. The use of such longer orifice plates having high density, i.e., closely-spaced, orifices generally requires mounting structures such as that described in commonly-owned U.S. Ser. No. 879,049 to Sutera, filed June 26, 1986, the disclosure of which is also incorporated herein by reference. Typically, the fluid-jet printing assembly and related mounting structure include a manifold assembly which defines upper and lower fluid subchambers, the latter of which includes an outlet slot for the printing fluid to pass through a linear array of orifices in the orifice plate.
One problem which exists with respect to fluid-jet printing devices, particularly those using longer orifice plates and closely-spaced orifices, is that during periods of shutdown, excess printing fluid may accumulate in and around the "active surfaces" of the print head such as the exterior surface of the orifice plate and/or its associated mounting structure. On occasion, the excess printing fluid may "mist out" on portions of the charging electrode and/or the deflection electrode structure and, if not removed, may ultimately cause the electrodes to short or otherwise adversely affect the performance of the ink jet printer. In addition, during shutdown periods, ink droplets which remain on the exterior surface of the orifice plate and associated mounting structure may dry and form solid particles and/or ink residue in and around the orifices, again adversely affecting the printing operation. Such undesirable ink residues and particulates may ultimately clog the orifices or become deposited on the printed substrate. Thus, their presence in the system should be avoided if possible.
Although it is known that an orifice plate may be cleaned periodically or between successive printing operations in order to avoid the above problems, the use of longer orifice plate constructions has resulted in an additional unexpected problem. The active surfaces of the ink jet printer which require cleaning, particularly the exterior surfaces of the orifice plate and associated mounting structure, are often inaccessible and cannot be effectively cleaned without the entire structure being disassembled in a costly and time consuming procedure. Heretofore, the surface of an orifice plate such as that described in commonly-owned Ser. No. 428,490 could be cleaned and/or purged only after the orifice plate had been removed or the print head at least partially disassembled to permit access to the plate and fluid manifold assembly. For example, excess fluid has been removed by swabbing or contacting the plate with fabric, sponges or other absorbent materials, both with and without cleaning solvents. However, before employing such manual techniques, the entire print head structure must generally be dismantled.
It is also known to use a suction device for purposes of removing excess ink in an around an orifice plate. Again, however, such devices have been useful only after the orifice plate or its associated mounting structure has been physically removed from the printer, thereby resulting in a cumbersome and time consuming separate cleaning operation. Conventional suction devices are also unacceptable for assembled structures, particularly printers having longer orifice plates, since they are incapable of reaching the various inaccessible active surfaces in and around the orifice plate.
The present invention substantially eliminates the above problems by providing a cleaning tool which eliminates the need to dismantle the print head, thus avoiding the time consuming procedures associated with conventional orifice cleaning techniques. In particular, the unique configuration and adjusting means used with the suction device in accordance with the present invention provides a more efficient tool for manually removing excess printing fluid from the exposed face of the fluid-jet orifice plate, without any need to physically remove the orifice plate from the print head. In addition, the entire cleaning operation can be conducted in a shorter period of time and in a more thorough manner than conventional techniques.
It has now been found that excess printing liquid can be removed from the vicinity of the orifice plate using adjustable suction means which are selectively applied to the active surfaces of the print head. In the preferred embodiment of the invention, the operative end of the cleaning device includes an elongated cylindrically-shaped head comprised of an elastomeric material having a generally beveled configuration at one end, i.e. tapered toward the open end thereof, and sized to fit in the area defined by the orifice plate and its associated mounting structure. The elongated head also contains a suction cavity which terminates in a centrally located exit port which, in turn, connects to a suction source via a uniquely configured fluid conduit.
The beveled (tapered) end of the vacuum head includes side wall portions which define an orifice plate contact surface inclined at an acute angle to the longitudinal axis of the elongated elastomeric vacuum head. The side portions terminate in a front surface generally perpendicular to the longitudinal axis of the vacuum head to define a nose portion. The preferred embodiment of the invention also utilizes a pair of angular notches in the form of V-shaped cut-out portions on each of the side walls which provide bending flexibility to the elongated head when pressure is exerted on the nose portion as the cleaning head makes contact with the orifice plate during a cleaning operation.
An alternative embodiment of the present invention utilizes an elongated head having a generally frusto-conical configuration, again sized to fit in the area defined by the orifice plate and its associated mounting structure. The frusto-conical head also contains a suction cavity. However, unlike the first embodiment, the head is surrounded by a peripheral skirt comprised of an elastomeric material which forms a pair of opposing vacuum lips having a laterally extending opening therethrough. The bottom of the suction cavity terminates in a centrally located exit port which, in turn, connects to a suction source via the fluid conduit.
A third embodiment of the present invention utilizes a rotatably mounted vacuum head having a generally rectangular, block-like configuration. With this particular embodiment, the vacuum head does not make direct contact with the orifice plate but instead traverses along the surface of the orifice plate clamp members and orifice plate corridor during a normal cleaning operation.
One important aspect of the present invention relates to the means for rotatably and angularly adjusting the position of the vacuum head. The adjusting means includes a rigid handle or "wand" formed from the fluid conduit having a configuration which is specially designed to avoid the structural orifice plate mounting components associated with the fluid-jet device. The unique configuration of the handle also permits the operator to "feel", without necessarily viewing, the relative position of the elongated vacuum head as it traverses the exposed surfaces of the orifice plate and its associated mounting structure. Because access to the exposed surfaces of the orifice plate is restricted, an operator may thereby use the invention to clean the entire orifice plate without actually viewing individual sections of the plate and/or its mounting structure. The rigid handle is configured to have a curved portion which avoids any obstruction with the surrounding mounting structure and a straight handle portion which may be manually grasped by the operator to manipulate the head along the exposed surface of the orifice plate. Preferably, the straight handle portion is disposed along an axis which angularly intersects the center point of the cleaning head exit port.
Thus, one object of the cleaning apparatus according to the present invention is to provide a more efficient method for manually removing excess or unwanted fluid from the active surfaces of a fluid-jet print head, including the exposed face of the fluid-jet orifice plate and its associated mounting components.
It is a further object of the present invention to provide a means for removing excess liquid from portions of the orifice plate and associated structure which are otherwise inaccessible.
It is still a further object of the present invention to provide a method and apparatus for cleaning the orifice plate without the time consuming conventional procedure of dismantling the existing print head structure.
Further aspects and advantages of the present invention will become more clear to the reader after careful consideration is given to the detailed description of the preferred exemplary embodiments which follow.